JP2001231169A - Compensating device for unbalanced load in distribution system and building facility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate inconveniences, such as incapability to make reliable compensation against load fluctuation, which are encountered when an unbalanced load of a distribution system is compensated on the distribution system side. SOLUTION: A consumer to whom power is distributed through a low-voltage distribution line is provided with a storage battery BAT for power storage and a power conditioner PC. The power conditioner is provided with power converting means (CON, TR, FIL, etc.), capable of bidirectionally converting power between the alternating current of the low-voltage distribution line and the storage battery and a control circuit C therefor. Unbalanced line voltage or line current or unbalanced line voltage and line current that may be produced in the low-voltage distribution line is compensated in parallel. Constitution based on a combination of the storage battery and privately owned electrical power facilities, power conversion wherein the power conditioner charges the storage battery with midnight power, constitution wherein power conversion of supplying power from the storage battery or privately owned electrical power facilities to the low-voltage distribution line, and constitution wherein the power conditioner suppresses higher harmonies produced in the low-voltage distribution line are also included.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an unbalanced load compensator and a building facility for balancing a three-phase power distribution system that distributes power to a single-phase load.

[0002]

2. Description of the Related Art Household electric appliances (coolers,
Refrigerators, washing machines, microwave ovens, etc., and various electric appliances (medical appliances, lighting appliances, electric bulletin boards, etc.) are often single-phase loads when viewed from the power supply. On the other hand, since the power distribution system is a three-phase power distribution system, power is supplied from the power distribution system to a customer by a low-voltage single-phase two-wire system or a low-voltage single-phase three-wire system.

FIG. 3 shows a connection diagram of a low-pressure single-phase two-wire system.
A low-voltage (100V or 200V) single phase is obtained from two phases of the three-phase high-voltage distribution lines U, V, and W through the single-phase transformer TR1, and is distributed to consumers. FIG. 4 shows a connection diagram of a low-voltage single-phase three-wire system, which is a single-phase transformer TR2 having a winding middle point on the secondary side, and a low-voltage (100 V and 20 V) between the winding middle point and both ends.
0 V) Obtain a single phase. FIG. 5 shows a connection diagram of a low-voltage three-phase four-wire system, which is drawn out with four wires using transformers TR1 and TR2.
Obtain three-phase 200V or single-phase 100V.

[0004] In these connection systems, for the three-phase high-voltage side,
The customer has a connection structure that takes in a single-phase unbalanced load. For this reason, the power supply system originally transmits and distributes three-phase parallel electric power using a three-phase generator, but many of the household electric appliances and various electric appliances of a customer have a single-phase load, and are not viewed from the high voltage side. It becomes a balanced load.

In addition, many of recent home electric appliances and various electric appliances have been increased in size, capacity, and function, and have a single-phase power consumption. Become.

As a countermeasure, a single-phase load is distributed to a three-phase power supply, and unbalanced voltage fluctuation due to a single-phase 100V → single-phase 200V is reduced. Further, as a special countermeasure shown in FIG. Thus, the equilibration is performed by the three-phase Scott transformer.

[0007]

The conventional countermeasures against unbalanced loads have the following problems because the fluctuations in the load become fluctuations in the amount of unbalanced load and the unbalanced load cannot be reliably eliminated.

If the generator voltage is increased to increase the lowest line voltage among the three phases in response to the occurrence of an unbalanced load, the highest line voltage may become an overvoltage.

Also, the existence of an unbalanced load means that, for example, when the current of two phases out of three phases approaches the overcurrent level, the remaining phases have a current margin but cannot supply any more power. In general, the efficiency of equipment use is reduced.

In addition, the presence of an unbalanced load causes a negative-phase current to flow through the rotor due to the characteristics of the generator, which becomes an extra current in the generator. Power generation equipment cannot be used effectively.

Similarly, when an unbalanced load is present, when the load includes a motor, its exciting current becomes unbalanced, and the motor is overheated or an original torque output cannot be obtained.

As another countermeasure against unbalance in the distribution system,
There is a method in which an active filter is installed at the connection point between the distribution system and the load, and compensation is performed collectively on the high voltage side. However, in this method, an active filter capable of predicting an unbalanced load amount to be generated and supplying a compensation current with a margin to it is provided.
That is, it is necessary to provide a large-sized active filter having a large compensation power capacity, and the use efficiency of the equipment deteriorates depending on a change in the unbalanced load amount.

The object of the present invention is to provide
An object of the present invention is to provide an unbalanced load compensating device and a building facility capable of reliably eliminating an unbalanced load and effectively using the device.

The building equipment includes individual building equipment such as hospitals and shops, as well as individual houses and collective housing, as well as an integrated building in which these individual buildings are integrated as a region.

[0015]

According to the present invention, an unbalanced load is provided as an unbalanced load compensating device for each customer (building facility) which is a source of the unbalanced load, and the device is a storage battery for power storage which can also use midnight power. By providing a power conditioner capable of bidirectional power conversion between the storage battery and the low-voltage distribution line, the customer himself compensates for the unbalanced load generated by the customer himself. If the customer has their own power generation facilities, charging the power storage batteries or supplying power to the distribution lines should be performed separately or in parallel. This is characterized by the following configuration.

An unbalanced load compensator for a distribution system for distributing a single-phase power from a three-phase high-voltage distribution line to a customer on a low-voltage distribution line side through a pole transformer, comprising: a DC power source provided by the customer; Provided between the low-voltage distribution line side and the DC power supply,
A power conversion unit capable of bidirectionally converting power between the three-phase AC of the low-voltage distribution line and the DC of the DC power supply, and a control unit therefor;
An unbalanced load compensator, comprising: a power conditioner for compensating in parallel for unbalance of line voltage or line current or line voltage and line current generated in the low-voltage distribution line. .

[0017] Further, there is provided a building facility for receiving a single-phase power from a low-voltage distribution line passing through a pole transformer from a three-phase high-voltage distribution line, comprising: a DC power supply provided by the building facility; A power conversion means provided between the DC power supply and capable of bidirectionally converting power between the three-phase AC of the low-voltage power distribution line and the direct current of the DC power supply, and a control means therefor; A building facility comprising: a power conditioner that compensates for imbalance between line voltage or line current or imbalance between line voltage and line current in parallel.

Further, the DC power supply is characterized in that it has a configuration in which only a storage battery for power storage is provided, or a configuration in which the storage battery is combined with a private power generation facility owned by a customer.

The power conditioner is configured to perform power conversion for charging the storage battery with midnight power of a power distribution system and power conversion for supplying power to the low-voltage distribution line with power from the storage battery or the private power generation facility. And

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the configuration of an apparatus according to an embodiment of the present invention, which is applied to a low-pressure three-phase three-wire system.

The power conditioner PC is connected to a low-voltage distribution line that distributes power from the low-voltage three-phase distribution line obtained at the pole transformer TR3 to each customer such as an apartment house. The power conditioner PC includes a sealed lead-acid battery BAT as a DC power supply for power storage, and an unbalanced current or voltage by a bidirectional AC-DC power conversion function with a low-voltage distribution line.
Alternatively, the unbalanced current and the voltage are compensated in parallel.

As a circuit means for this compensation, a three-phase transformer TR and a filter FI are provided between the distribution line and the storage battery BAT.
It includes a main circuit including L, a converter CON, and a switch (such as a circuit breaker), and a control circuit C for controlling the converter CON.

The transformer TR is made up of three-phase three-windings to step up or down the three-phase current. Converter CON is IGBT
A power conversion circuit is configured using a power semiconductor switch such as a switch as a switching means, and performs forward conversion for converting AC power from the transformer TR into DC power and reverse conversion for converting DC power from the storage battery BAT into AC power. The filter FIL removes a harmonic component generated when the converter CON performs an inverse conversion operation, and removes a noise component that enters from the transformer TR side.

The control circuit C controls the unbalance compensation voltage generated by the converter CON in the reverse conversion operation according to the unbalance amount of the three-phase line voltage detected by the detector transformer PT. Further, the control circuit C uses the three-phase voltage detected by the instrument transformer PT as a reference phase, and the unbalance compensation current generated by the converter CON in reverse conversion according to the unbalance amount of the three-phase line current detected by the current transformer CT. Control. Further, the control circuit C simultaneously controls both the unbalance compensation voltage and the unbalance compensation current generated by the converter CON.

The control circuit C operates according to the charge / discharge current of the storage battery BAT detected by the current detector AM.
ON controls the charging current generated in the forward conversion.

In the above configuration, when the load on the consumer changes and the low-voltage distribution line becomes unbalanced, the control circuit C of the power conditioner PC changes the transformer PT or the current transformer C.
Detects an unbalanced load amount from T, switches between forward conversion and reverse conversion of the converter CON, and performs current control for each line.
To balance the three-phase voltage or three-phase current of the low-voltage distribution line,
Alternatively, compensation power corresponding to the unbalanced load amount is exchanged between the distribution line and the storage battery BAT so that both the current and the voltage are balanced.

Therefore, when the unbalanced load amount fluctuates due to the fluctuation of the load of the customer, the unbalanced load can be surely compensated by the power conditioner PC according to the unbalanced load amount.

Moreover, since the unbalanced load compensation is performed individually on the customer side which is the source of the unbalanced load, the power capacity required for the compensation is minimized and the use of the unbalanced load compensator is performed. Efficiency can be increased. For example, when the electric load is included in the load on the consumer side, the unbalanced load can be compensated without hindering the operation. In addition, line voltage control on the high-voltage distribution line side and unbalanced load compensation using an active filter are not required, and the efficiency of equipment utilization for power distribution on the high-voltage distribution line side can be increased, and adverse effects on generators, etc. Has no effect.

It should be noted that whether to prioritize the line voltage balance or the line current balance in compensating for the unbalanced load is determined by giving priority to the load condition of the customer or changing the ratio. Can be determined by

Here, the storage battery BAT may be charged by an unbalanced current compensating operation, but can be performed by using the late-night power, which is reduced by the power conditioner PC. In this case, the power company can contribute to power leveling on the distribution line side as viewed from the power company, and the customer who generates the unbalanced load can suppress the power rate while compensating for the unbalanced load.

It should be noted that after receiving the cheap midnight power, this AC power is converted to DC by a charger to charge the storage battery, and
An apparatus has been proposed in which the DC power of the storage battery is inversely converted to AC power by an inverter and used as daytime power (Utility Model Registration No. 3045189). Since this device uses late-night power, which has less power demand, it can reduce the daytime load when the consumer load increases,
It is conceivable to use the imbalance of the distribution system as a countermeasure.

However, it is not specified which of the three phases of the power distribution system is connected to a consumer who uses midnight power, and fluctuations occur. Conversely, unbalanced load may increase. In this regard, in this embodiment, an unbalanced state is detected,
Based on this detection, equilibrium can be ensured by the power conditioner.

Next, as a DC power supply of the power conditioner CON, in addition to the storage battery BAT, private power generation equipment such as a solar cell equipment G1, a fuel cell equipment G2, a wind power generator equipment G3, and an emergency private power generator. When it is provided, the received power can be suppressed low by charging the storage battery BAT with these private power generation facilities. In addition, when there is surplus power in the private power generation equipment, the power conditioner P
C can be supplied to consumers as self-sufficient power.

When these private power generation facilities are provided, solar energy or the like can be effectively used to compensate for the unbalanced load, and can contribute to prevention of global warming due to the environment and CO ₂ .

The embodiment shows a case where a DC power supply and one power conditioner are provided on the secondary side of the pole transformer TR3 which distributes power to a plurality of consumers such as an apartment house. The same effect can be obtained when a DC power supply and a power conditioner are provided for each customer, and when a DC power supply and one power conditioner are provided for an integrated building that integrates buildings as a region, including hospitals and stores. Obtainable.

In the embodiment, a case where the present invention is applied to a low-pressure single-phase three-wire system is shown. However, the present invention can be applied to a low-pressure single-phase two-wire system and a low-pressure three-phase four-wire system. FIG. 2 shows a case where the present invention is applied to a low-voltage three-phase four-wire system, and the power conditioner PC and the like have the same configuration.

Further, the power conditioner PC can basically have a harmonic suppression function similarly to a conventional active filter.

[0038]

As described above, according to the present invention, an unbalanced load compensating device is provided for each customer (building facility), and a direct current power supply having a storage battery for power storage and a private power generating facility is connected to the low-voltage distribution line. Since a power conditioner capable of bidirectional power conversion is provided between the consumers, the consumers themselves can compensate for the unbalanced load generated by the customers themselves. it can.

For the unbalanced load compensation, the unbalance of the line voltage of the distribution line or the unbalance of the line current can be compensated individually or in parallel.

If the customer has a private power generation facility, the storage battery can be charged or power can be supplied to the distribution line.

Further, by providing the power supply equipment for the consumer, a stable power supply can be secured without voltage drop due to unbalance of the power distribution system, and home equipment such as a personal computer may malfunction due to a drop in the power supply voltage. Inconvenience can be eliminated.

[Brief description of the drawings]

FIG. 1 is a configuration diagram (part 1) of an unbalanced load compensating device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram (part 2) of an unbalanced load compensator according to another embodiment of the present invention.

FIG. 3 is a power distribution system diagram of a low-voltage single-phase two-wire system.

FIG. 4 is a power distribution system diagram of a low-voltage single-phase three-wire system.

FIG. 5 is a power distribution system diagram of a low-voltage three-phase four-wire system.

FIG. 6 shows a single-phase load method using a Scott transformer connection.

[Explanation of symbols]

 TR1 to TR3: Pole transformer PC: Power conditioner CON: Converter BAT: Sealed lead-acid battery C: Control circuit G1: Solar power generation equipment G2: Fuel cell equipment G3: Wind power generator equipment

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshio Yoshida 2-1-17-1 Osaki, Shinagawa-ku, Tokyo Inside the Meidensha Corporation (72) Inventor Seiji Harada 2-1-1-17 Osaki, Shinagawa-ku, Tokyo Stock Association F-term (reference) in the company Meidensha 5G066 GA02 GC01

Claims (6)

[Claims] 1. An unbalanced load compensator for a distribution system that distributes a single-phase power from a three-phase high-voltage distribution line to a customer on a low-voltage distribution line side through a pole transformer, wherein the direct-current power supply installed in the customer is provided. And a power conversion unit provided between the low-voltage distribution line side and the DC power supply, and capable of bidirectionally converting power between the three-phase AC of the low-voltage distribution line and the DC of the DC power supply, and a control unit therefor. A power conditioner for compensating in parallel the unbalance of the line voltage or the line current generated in the low-voltage distribution line or the unbalance of the line voltage and the line current. Load compensator. 2. The unbalanced distribution system according to claim 1, wherein the DC power supply has a configuration in which only a storage battery for power storage is provided, or a configuration in which the storage battery and a private power generation facility owned by a customer are combined. Load compensator. 3. The power conditioner is configured to perform power conversion for charging the storage battery with midnight power of a power distribution system and power conversion for supplying power to the low-voltage distribution line with power from the storage battery or the private power generation facility. The unbalanced load compensator for a distribution system according to claim 1 or 2, wherein 4. A building facility for receiving a single-phase power from a low-voltage distribution line passing through a pole transformer from a three-phase high-voltage distribution line, comprising: a DC power supply provided by the building facility; A power conversion means provided between the DC power supply and capable of bidirectionally converting power between the three-phase AC of the low-voltage power distribution line and the direct current of the DC power supply, and a control means therefor; A building facility comprising: a power conditioner that compensates for imbalance between line voltage or line current or imbalance between line voltage and line current in parallel. 5. The building equipment according to claim 4, wherein the DC power supply has a configuration in which only a storage battery for power storage is provided, or a configuration in which the storage battery and a private power generation facility of a building are combined. 6. The power conditioner is configured to perform power conversion for charging the storage battery with midnight power of a power distribution system and power conversion for supplying power to the low-voltage distribution line with power from the storage battery or the private power generation facility. The building equipment according to claim 4 or 5, wherein: